regex: avoid infinite configure test

At least glibc 2.15 on Ubuntu ended up hanging.

* m4/regex.m4 (gl_REGEX): Add an alarm escape hatch.
Reported by Reuben Thomas.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/ChangeLog b/ChangeLog
index c18cbad..74dad7e 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2013-01-31  Eric Blake  <eblake@redhat.com>
+
+       regex: avoid infinite configure test
+       * m4/regex.m4 (gl_REGEX): Add an alarm escape hatch.
+
 2013-01-31  Reuben Thomas  <rrt@sc3d.org>
 
        openpty: fix bug where HAVE_OPENPTY wasn't defined

diff --git a/m4/regex.m4 b/m4/regex.m4
index 2f5bd09..944dfaf 100644 (file)
--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,4 +1,4 @@
-# serial 62
+# serial 63
 
 # Copyright (C) 1996-2001, 2003-2013 Free Software Foundation, Inc.
 #
@@ -27,6 +27,7 @@ AC_DEFUN([gl_REGEX],
     # following run test, then default to *not* using the included regex.c.
     # If cross compiling, assume the test would fail and use the included
     # regex.c.
+    AC_CHECK_FUNCS_ONCE([alarm])
     AC_CACHE_CHECK([for working re_compile_pattern],
                    [gl_cv_func_re_compile_pattern_working],
       [AC_RUN_IFELSE(
@@ -35,6 +36,10 @@ AC_DEFUN([gl_REGEX],
            #include <locale.h>
            #include <limits.h>
            #include <regex.h>
+           #if HAVE_ALARM
+           # include <unistd.h>
+           # include <signal.h>
+           #endif
            ]],
           [[int result = 0;
             static struct re_pattern_buffer regex;
@@ -43,6 +48,11 @@ AC_DEFUN([gl_REGEX],
             const char *s;
             struct re_registers regs;
 
+#if HAVE_ALARM
+            /* Some builds of glibc go into an infinite loop on this test.  */
+            signal (SIGALRM, SIG_DFL);
+            alarm (2);
+#endif
             if (setlocale (LC_ALL, "en_US.UTF-8"))
               {
                 {